U.S. patent application number 14/497012 was filed with the patent office on 2015-10-22 for dielectric and method for producing the same, and electrolytic capacitor.
The applicant listed for this patent is NEC Tokin Corporation. Invention is credited to Yuji Murayama, Koji Sakata, Yasuhisa Sugawara.
Application Number | 20150299887 14/497012 |
Document ID | / |
Family ID | 54321518 |
Filed Date | 2015-10-22 |
United States Patent
Application |
20150299887 |
Kind Code |
A1 |
Murayama; Yuji ; et
al. |
October 22, 2015 |
DIELECTRIC AND METHOD FOR PRODUCING THE SAME, AND ELECTROLYTIC
CAPACITOR
Abstract
There are provided a dielectric and an electrolytic capacitor
that have a small amount of leakage current, and have high
reliability also in a high temperature environment. A dielectric
containing at least zirconium, titanium, and a carbon atom, wherein
a concentration of the carbon atom is 100 ppm or more and 10,000
ppm or less, and an atomic ratio of the titanium to a sum of the
zirconium and the titanium is 30% or more and 90% or less.
Inventors: |
Murayama; Yuji; (Sendai-shi,
JP) ; Sakata; Koji; (Sendai-shi, JP) ;
Sugawara; Yasuhisa; (Sendai-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NEC Tokin Corporation |
Sendai-shi |
|
JP |
|
|
Family ID: |
54321518 |
Appl. No.: |
14/497012 |
Filed: |
September 25, 2014 |
Current U.S.
Class: |
428/548 ;
148/237; 205/209; 420/417; 420/422 |
Current CPC
Class: |
C22C 14/00 20130101;
C23C 8/44 20130101; C22C 16/00 20130101; C23C 8/20 20130101; C25D
11/26 20130101 |
International
Class: |
C25D 9/06 20060101
C25D009/06; C25D 11/34 20060101 C25D011/34; C22C 14/00 20060101
C22C014/00; C23C 8/20 20060101 C23C008/20; C22C 16/00 20060101
C22C016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 22, 2014 |
JP |
2014-088038 |
Claims
1. A dielectric comprising at least zirconium, titanium, and a
carbon atom, wherein a concentration of the carbon atom is 100 ppm
or more and 10,000 ppm or less, and an atomic ratio of the titanium
to a sum of the zirconium and the titanium is 30% or more and 90%
or less.
2. A method for producing the dielectric according to claim 1,
comprising: mixing an alloy of zirconium and titanium with an
organic binder to obtain a mixture; sintering the mixture to obtain
a sintered body; and anodizing the sintered body.
3. The method for producing the dielectric according to claim 2,
wherein the organic binder is at least one selected from the group
consisting of an acrylic resin, a polyvinyl alcohol resin, a
styrenic resin, and camphor.
4. A method for producing the dielectric according to claim 1,
comprising: heat-treating an alloy of zirconium and titanium in a
gas comprising organic compound A; and anodizing the alloy after
the heat treatment.
5. A method for producing the dielectric according to claim 1,
comprising: anodizing an alloy of zirconium and titanium in a
solution comprising organic compound B.
6. A dielectric produced by the method according to claim 2.
7. A dielectric produced by the method according to claim 3.
8. A dielectric produced by the method according to claim 4.
9. A dielectric produced by the method according to claim 5.
10. An electrolytic capacitor comprising the dielectric according
to claim 1.
11. An electrolytic capacitor comprising the dielectric according
to claim 6.
12. An electrolytic capacitor comprising the dielectric according
to claim 7.
13. An electrolytic capacitor comprising the dielectric according
to claim 8.
14. An electrolytic capacitor comprising the dielectric according
to claim 9.
Description
[0001] This application is based upon and claims the benefit of
priority from Japanese patent application No. 2014-88038, filed on
Apr. 22, 2014, the disclosure of which is incorporated herein in
its entirety by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a dielectric and a method
for producing the same, and an electrolytic capacitor.
[0004] 2. Description of the Related Art
[0005] An oxide containing a valve metal is mainly used for a
dielectric forming the dielectric layer of an electrolytic
capacitor. The oxide has valve action, has a high dielectric
constant, and can achieve higher capacitance. Techniques related to
dielectrics are disclosed in JP1-277342A, JP2010-34589A,
JP43-18012B, JP6-333263A, JP9-165676A, JP2004-22702A, and
JP2005-327428A.
[0006] However, in the techniques described in the above patent
literatures, the amount of leakage current is large, and
particularly in a high temperature environment, there is a tendency
that the increase fluctuation of capacitance increases, and the
leakage current increases, and therefore, the reliability is
low.
[0007] It is an object of the present invention to provide a
dielectric and an electrolytic capacitor that have a small amount
of leakage current, and have high reliability also in a high
temperature environment.
SUMMARY OF THE INVENTION
[0008] A dielectric according to the present invention is a
dielectric containing at least zirconium, titanium, and a carbon
atom, wherein a concentration of the carbon atom is 100 ppm or more
and 10,000 ppm or less, and an atomic ratio of the titanium to a
sum of the zirconium and the titanium is 30% or more and 90% or
less.
[0009] A method for producing a dielectric according to the present
invention includes mixing an alloy of zirconium and titanium with
an organic binder to obtain a mixture; sintering the mixture to
obtain a sintered body; and anodizing the sintered body.
[0010] A method for producing a dielectric according to the present
invention includes heat-treating an alloy of zirconium and titanium
in a gas containing organic compound A; and anodizing the alloy
after the heat treatment.
[0011] A method for producing a dielectric according to the present
invention includes anodizing an alloy of zirconium and titanium in
a solution containing organic compound B.
[0012] An electrolytic capacitor according to the present invention
includes the dielectric according to the present invention.
[0013] The present invention can provide a dielectric and an
electrolytic capacitor that have a small amount of leakage current,
and have high reliability also in a high temperature
environment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Dielectric
[0014] A dielectric according to the present invention is a
dielectric containing at least zirconium (Zr), titanium (Ti), and
carbon atoms (C), wherein the concentration of the carbon atoms is
100 ppm or more and 10,000 ppm or less, and the atomic ratio of the
titanium to the sum of the zirconium and the titanium (Ti/(Zr+Ti))
is 30% or more and 90% or less.
[0015] Ti has a relative dielectric constant exceeding those of Ta
and Al, and therefore, its application to electrolytic capacitors
is regarded as promising. However, an oxide that is a dielectric
containing Ti is likely to crystallize, and therefore, a problem of
the oxide is that the leakage current is likely to increase.
Therefore, it is considered that a different element is added to Ti
for alloying to suppress crystallization. However, for example, in
a dielectric obtained using an alloy containing Ti and Zr, or Ti
and Al, the leakage current is not sufficiently reduced, and the
dielectric cannot be applied to an electrolytic capacitor. In
addition, for the dielectric, in a high temperature environment,
the increase fluctuation of capacitance increases, and the leakage
current also increases because in a high temperature environment,
oxygen atoms in the oxide that is the dielectric diffuse to the
underlying valve metal side, and the effective thickness of the
dielectric film decreases.
[0016] The dielectric according to the present invention contains
zirconium, titanium, and carbon atoms at a particular ratio. In the
present invention, the carbon atoms added in a slight amount can
suppress the crystallization of the dielectric and stabilize the
amorphous structure. Thus, a dielectric having a small amount of
leakage current can be obtained. In addition, also in a high
temperature environment, the carbon atoms added in a slight amount
inhibit the movement of oxygen, and therefore, an increase in the
increase fluctuation of capacitance and an increase in leakage
current can be suppressed, and a dielectric having high reliability
can be obtained. In this manner, the dielectric according to the
present invention is useful as a dielectric for an electrolytic
capacitor.
[0017] The concentration of carbon atoms in the dielectric
according to the present invention is 100 ppm or more and 10,000
ppm or less. When the concentration of carbon atoms is less than
100 ppm, a sufficient crystallization suppression effect is not
obtained, and the leakage current increases. On the other hand,
when the concentration of carbon atoms exceeds 10,000 ppm, a
carbide is formed to provide a dielectric having low insulating
properties, and the leakage current increases. The concentration of
carbon atoms is preferably 150 ppm or more and 8,000 ppm or less,
more preferably 1,000 ppm or more and 7,000 ppm or less, and
further preferably 2,000 ppm or more and 5,000 ppm or less. The
measurement of the concentration of carbon atoms is carried out by
a method described later. In addition, "ppm," the unit of the
concentration of carbon atoms, is a mass ratio.
[0018] The atomic ratio of the titanium to the sum of the zirconium
and the titanium included in the dielectric according to the
present invention is 30% or more and 90% or less. When the atomic
ratio is less than 30%, the dielectric is a crystalline oxide and
is not an amorphous structure. On the other hand, when the atomic
ratio exceeds 90%, the dielectric changes from the amorphous
structure to the crystalline oxide at low anodization voltage when
the dielectric is produced by anodization described later. The
atomic ratio is preferably 33% or more and 70% or less, more
preferably 35% or more and 60% or less, and further preferably 37%
or more and 50% or less. The measurement of the atomic ratio is
carried out by a method described later.
[0019] The dielectric according to the present invention can be in
a state in which carbon atoms are dissolved in an oxide containing
zirconium and titanium. The state can be confirmed by XPS (X-ray
photoelectron spectroscopy) and an EPMA (Electron probe micro
analyzer).
[0020] The dielectric according to the present invention preferably
includes an amorphous structure. When the dielectric includes an
amorphous structure, the leakage current decreases. The fact that
the dielectric includes an amorphous structure can be confirmed by
a transmission electron microscope.
[0021] The dielectric according to the present invention may also
contain a different element such as nitrogen atoms, fluorine atoms,
or phosphorus atoms in addition to zirconium, titanium, and carbon
atoms. Also when the dielectric contains the different element, the
effects of the suppression of the crystallization of the dielectric
and the inhibition of the diffusion of oxygen are obtained. The
different element may be included in the dielectric at 10000 ppm or
less and is preferably not included in the dielectric. The
dielectric according to the present invention can contain oxygen
atoms.
[0022] [Methods for Producing Dielectrics]
[0023] The dielectric according to the present invention can be
preferably produced by embodiments shown below.
[0024] The concentration of carbon atoms in each of dielectrics
obtained by methods according to the embodiments shown below is 100
ppm or more and 10,000 ppm or less. In a dielectric oxide film
containing carbon atoms at the above concentration, the carbon
atoms present dissolved in the film stabilize the amorphous
structure of the oxide, and therefore, the leakage current is
reduced. Further, in a high temperature environment, the carbon
atoms present dissolved inhibit the diffusion of oxygen atoms in
the dielectric oxide film into a metal layer that is a substrate,
and therefore, an electrolytic capacitor having high reliability in
which an increase in the increase fluctuation of capacitance and an
increase in leakage current are suppressed is obtained. Also when
no raw material for carbon atoms is intentionally added during
dielectric fabrication, carbon atoms may be included as an impurity
in zirconium and titanium at less than 100 ppm. However, the amount
of the carbon atoms included as an impurity is small, and
therefore, the concentration of carbon atoms in the dielectric is
not 100 ppm or more unless a raw material for carbon atoms is
intentionally added during dielectric fabrication.
[0025] In addition, the atomic ratio of titanium to the sum of
zirconium and titanium in each of the dielectrics obtained by the
above methods is 30% or more and 90% or less. When the atomic ratio
is within the above range, a dielectric oxide film formed by
anodization is likely to be an amorphous structure and is less
likely to be a crystalline oxide. On the other hand, when the
atomic ratio is outside the above range, a sufficient
crystallization suppression effect of carbon atoms is not obtained,
and an amorphous structure is not provided even if the dielectric
contains carbon atoms at a concentration within the above
range.
[0026] The dielectric according to the present invention is not
limited to the dielectrics produced by the following
embodiments.
First Embodiment
[0027] A method for producing a dielectric according to this
embodiment includes mixing an alloy of zirconium and titanium with
an organic binder to obtain a mixture; sintering the above mixture
to obtain a sintered body; and anodizing the above sintered body.
According to the method, an underlying metal in which carbon atoms
are present dissolved is anodized, and therefore, the dielectric
containing carbon atoms according to the present invention is
easily obtained.
[0028] In the above method, first, an alloy of zirconium and
titanium and an organic binder are mixed to obtain a mixture
(hereinafter also shown as a mixing step). The atomic ratio of the
zirconium to the titanium included in the alloy preferably
satisfies the range of the atomic ratio of zirconium to titanium
according to the present invention. As the alloy, for example, a
powder of an alloy of zirconium and titanium can be used. As the
organic binder, acrylic resins, polyvinyl alcohol resins, styrenic
resins, camphor, and the like are preferred in terms of reactivity
with the alloy of zirconium and titanium during sintering described
later. These may be used singly or in combinations of two or more.
Among these, acrylic resins are more preferred as the organic
binder in terms of the strength of a pressure-press formed body.
The organic binder contains carbon atoms and therefore is a raw
material for the carbon atoms of the dielectric. For the mixing
ratio of the above alloy to the above organic binder, when the
amount of the above alloy is 100 parts by mass, the amount of the
above organic binder is preferably 0.1 parts by mass or more and 40
parts by mass or less, more preferably 1 part by mass or more and
30 parts by mass or less, in terms of the suitable range of the
amount of carbon atoms included in the dielectric. The method for
mixing the above alloy and the above organic binder is not
particularly limited, and they can be mixed using, for example, a
blade type mixer. The fact that the zirconium and the titanium are
alloyed can be confirmed by an X-ray diffraction method.
[0029] Next, the above mixture is sintered to obtain a sintered
body (hereinafter also shown as a sintering step). In this step,
most of the organic binder is gasified, but some carbon atoms in
the organic binder react with the alloy of titanium and zirconium,
and therefore, the alloy of titanium and zirconium containing a
certain amount of carbon atoms is formed on the surface. In
addition, when the above mixture is powdery, the obtained sintered
body is porous. In terms of the suitable range of the amount of
carbon atoms included in the dielectric, the sintering temperature
is preferably 400.degree. C. or more and 1200.degree. C. or less,
more preferably 500.degree. C. or more and 1000.degree. C. or less,
and further preferably 600.degree. C. or more and 800.degree. C. or
less. In addition, the sintering time is preferably 5 minutes or
more and 3 hours or less, more preferably 15 minutes or more and 1
hour or less, and further preferably 20 minutes or more and 40
minutes or less. The sintering is preferably performed under
reduced pressure, more preferably under vacuum.
[0030] Press forming the above mixture (hereinafter also shown as a
press forming step) may be performed between the above mixing step
and the above sintering step. For example, a press formed body can
be fabricated by filling a die with the above mixture together with
metal wire containing a valve metal, and pressure-press forming
them. When the press forming step is performed, the obtained press
formed body is sintered by the above sintering step to obtain a
sintered body.
[0031] Next, the above sintered body is anodized. The anodization
can be performed in a solution containing an electrolyte using the
above sintered body as an anode. For this solution, aqueous
solutions and nonaqueous solutions containing phosphoric acid,
nitric acid, boric acid, citric acid, and sodium salts and ammonium
salts thereof, and the like can be used. These may be used singly
or in combinations of two or more. The concentration of the
electrolyte in the solution can be 0.001% by mass or more and 80%
by mass or less and is preferably 0.005% by mass or more and 1% by
mass or less. The voltage of the anodization is preferably 1 V or
more and 1000 V or less, more preferably 3 V or more and 500 V or
less, and further preferably 50 V or more and 200 V or less. The
temperature of the solution in performing anodization is preferably
0.degree. C. or more and 100.degree. C. or less, more preferably
15.degree. C. or more and 95.degree. C. or less, and further
preferably 20.degree. C. or more and 40.degree. C. or less. By the
anodization, the above sintered body is oxidized, and the
dielectric according to the present invention is obtained.
Second Embodiment
[0032] A method for producing a dielectric according to this
embodiment includes heat-treating an alloy of zirconium and
titanium in a gas containing organic compound A; and anodizing the
alloy after the above heat treatment. According to the method, an
underlying metal in which carbon atoms are present dissolved is
anodized, and therefore, the dielectric containing carbon atoms
according to the present invention is easily obtained.
[0033] In the above method, first, an alloy of zirconium and
titanium is heat-treated in a gas containing organic compound A. In
this step, some of carbon atoms included in organic compound A are
incorporated into the alloy of zirconium and titanium, and the
alloy of titanium and zirconium containing a certain amount of
carbon atoms is formed on the surface. The atomic ratio of the
zirconium to the titanium included in the alloy of zirconium and
titanium preferably satisfies the range of the atomic ratio of
zirconium to titanium according to the present invention. As the
alloy, for example, a plate of an alloy of zirconium and titanium
can be used. The alloy plate can be fabricated by metallurgical
processes such as rolling and casting and methods such as
sputtering. The thickness of the alloy plate can be, for example,
100 nm to 1 mm. Examples of organic compound A include hydrocarbon
gases such as methane, propane, ethylene, and acetylene. These may
be used singly or in combinations of two or more. Among these,
methane is preferred as organic compound A in terms of reactivity.
When organic compound A is solid at the temperature of the heat
treatment, organic compound A may be dissolved in an appropriate
solvent and used as a liquid containing organic compound A.
[0034] Organic compound A may be diluted with an inert gas such as
nitrogen or argon (Ar). In this case, in terms of the suitable
range of the amount of carbon atoms included in the dielectric,
preferably 0.01 mole % or more and 100 mole % or less, more
preferably 0.1 mole % or more and 40 mole % or less, and further
preferably 0.5 mole % or more and 10 mole % or less of organic
compound A is included in the gas containing organic compound
A.
[0035] In terms of the suitable range of the amount of carbon atoms
included in the dielectric, the temperature of the heat treatment
is preferably 400.degree. C. or more and 1200.degree. C. or less,
more preferably 600.degree. C. or more and 1000.degree. C. or less,
and further preferably 800.degree. C. or more and 950.degree. C. or
less. In addition, the time of the heat treatment is preferably 1
minute or more and 3 hours or less, more preferably 15 minutes or
more and 1 hour or less, and further preferably 20 minutes or more
and 40 minutes or less.
[0036] Next, the alloy after the above heat treatment is anodized.
The anodization can be performed as in the above first embodiment.
By the anodization, the alloy after the above heat treatment is
oxidized, and the dielectric according to the present invention is
obtained.
Third Embodiment
[0037] A method for producing a dielectric according to this
embodiment includes anodizing an alloy of zirconium and titanium in
a solution containing organic compound B. According to the method,
carbon is introduced into an underlying metal simultaneously with
anodization, and therefore, the dielectric containing carbon atoms
according to the present invention is easily obtained.
[0038] In the above method, an alloy of zirconium and titanium is
anodized in a solution containing organic compound B. In this step,
some of carbon atoms included in organic compound B are
incorporated into the alloy of zirconium and titanium, and the
alloy of titanium and zirconium containing a certain amount of
carbon atoms is formed on the surface. As the alloy of zirconium
and titanium, the same one as the alloy of zirconium and titanium
in the above second embodiment can be used. Examples of organic
compound B include organic solvents such as ethylene glycol,
formamide, glycerin, and dimethyl sulfoxide. These may be used
singly or in combinations of two or more. Among these, ethylene
glycol is preferred as organic compound B in terms of safety and
cost. The solution containing organic compound B can contain a
solvent such as water or a nonaqueous solvent. In this case, in
terms of the suitable range of the amount of carbon atoms included
in the dielectric, preferably 0.01% by mass or more and less than
100% by mass, more preferably 0.1% by mass or more and 90% by mass
or less, and further preferably 30% by mass or more and 70% by mass
or less of organic compound B is included in the solution
containing organic compound B.
[0039] The anodization can be performed in a solution containing
the above organic compound B and an electrolyte using the above
alloy of zirconium and titanium as an anode. As the electrolyte,
phosphoric acid, nitric acid, boric acid, citric acid, and sodium
salts and ammonium salts thereof, and the like can be used. These
may be used singly or in combinations of two or more. The
concentration of the electrolyte in the solution can be 0.001% by
mass or more and 80% by mass or less and is preferably 0.005% by
mass or more and 1% by mass or less. In terms of the suitable range
of the amount of carbon atoms included in the dielectric, the
voltage of the anodization is preferably 1 V or more and 1000 V or
less, more preferably 3 V or more and 600 V or less, and further
preferably 50 V or more and 200 V or less. In addition, the
temperature of the solution in performing anodization is preferably
0.degree. C. or more and 100.degree. C. or less, more preferably
15.degree. C. or more and 95.degree. C. or less, and further
preferably 20.degree. C. or more and 40.degree. C. or less. By the
anodization, the above alloy of zirconium and titanium is oxidized
incorporating carbon atoms, and the dielectric according to the
present invention is obtained.
[0040] [Electrolytic Capacitor]
[0041] An electrolytic capacitor according to the present invention
includes the dielectric according to the present invention. The
electrolytic capacitor according to the present invention includes
for a dielectric layer a dielectric in which the leakage current is
low, and an increase in the increase fluctuation of capacitance and
an increase in leakage current can be suppressed also in a high
temperature environment, and therefore, the electrolytic capacitor
has high reliability. For example, the configuration of the
electrolytic capacitor according to the present invention is not
particularly limited as long as it includes the dielectric
according to the present invention for a dielectric layer. Known
configurations can be adopted. Examples of the configuration
include a configuration in which a cathode electrolyte such as
manganese dioxide is formed on the dielectric according to the
present invention, and a cathode layer including a graphite layer
and a silver paste layer is further formed on the cathode
electrolyte.
EXAMPLES
[0042] Examples of the present invention will be shown below, but
the present invention is not limited to these.
[0043] [Concentration of Carbon Atoms]
[0044] The measurement of the concentration of carbon atoms
included in a dielectric was carried out by a nondiffusive infrared
absorption method. The measurement was carried out using CS-444LS
(product name, manufactured by LECO).
[0045] [Atomic Ratio of Titanium to Sum of Zirconium and
Titanium]
[0046] The number of moles of each of zirconium and titanium
included in a dielectric was measured by an energy-dispersive X-ray
analysis method. The measurement was carried out using Genesis 2000
(product name, manufactured by EDAX). Using the measurement
results, the proportion of the number of moles of titanium to the
sum of numbers of moles of zirconium and titanium was calculated to
obtain the above atomic ratio.
[0047] [Leakage Current and Capacitance]
[0048] A dielectric obtained by anodization was washed with pure
water, and a voltage of 70 V was applied to the dielectric in the
same solution as during the anodization. Leakage current after 5
minutes from the start of the voltage application was measured
(hereinafter shown as leakage current after anodization). In
addition, capacitance was measured in a 5% by mass aqueous solution
of ammonium borate at a frequency of 120 Hz (hereinafter shown as
capacitance after anodization). Then, a high temperature storage
test in which the dielectric was stored at 150.degree. C. for 240
hours was performed. After the high temperature storage test,
leakage current (hereinafter shown as leakage current after the
high temperature storage test) and capacitance (hereinafter shown
as capacitance after the high temperature storage test) were
measured by the same methods as the above, respectively.
[0049] The rate of change of leakage current and the rate of change
of capacitance were calculated by the following formulas.
(the rate of change of leakage current)=(leakage current after the
high temperature storage test)/(leakage current after
anodization)
(the rate of change of capacitance)=(capacitance after the high
temperature storage test)/(capacitance after anodization)
[0050] In Table 1, leakage current after anodization is shown as a
converted value when the value in Comparative Example 2 is
1.00.
Example 1
[0051] 15 Parts by mass of an acrylic resin as an organic binder
was added to 100 parts by mass of a powder of an alloy of titanium
and zirconium (Ti:Zr=40:60 (atomic ratio)) to fabricate
agglomerates of the alloy powder. A die was filled with the
agglomerates together with metal wire containing an alloy of
titanium and zirconium, and they were pressure-press formed to
fabricate a press formed body having an outer shape of 2.2
mm.times.1.7 mm.times.1.2 mm. Next, the press formed body was
sintered in a vacuum at a high temperature of 600.degree. C. for 30
minutes to obtain a porous sintered body. At this time, most of the
acrylic resin added as the organic binder was pyrolyzed and
discharged as a gas, but the remainder reacted with the alloy
powder and remained. 100 V anodization was performed in an aqueous
solution containing phosphoric acid as an electrolyte at a
concentration of 0.01% by mass at a liquid temperature of
25.degree. C. using the porous sintered body as an anode to obtain
a dielectric. The results are shown in Table 1.
Example 2
[0052] A plate of an alloy of titanium and zirconium (Ti:Zr=40:60
(atomic ratio), 20 mm long.times.10 mm wide.times.0.1 mm thick) was
heat-treated in a mixed gas of methane and Ar (methane:Ar=1:99
(molar ratio)) at 900.degree. C. for 30 minutes to react some of
carbon atoms included in the methane with the alloy plate. Then,
100 V anodization was performed in an aqueous solution containing
phosphoric acid as an electrolyte at a concentration of 0.01% by
mass at a liquid temperature of 25.degree. C. using the alloy plate
as an anode to obtain a dielectric. The results are shown in Table
1.
Example 3
[0053] 100 V anodization was performed in a solution containing
phosphoric acid as an electrolyte at a concentration of 0.01% by
mass and containing each of water and ethylene glycol as a solvent
at a concentration of 50% by mass at a liquid temperature of
25.degree. C. using a plate of an alloy of titanium and zirconium
(Ti:Zr=40:60 (atomic ratio), 20 mm long.times.10 mm wide.times.0.1
mm thick) as an anode to obtain a dielectric. The results are shown
in Table 1.
Example 4
[0054] 100 V anodization was performed in a solution containing
phosphoric acid as an electrolyte at a concentration of 0.01% by
mass and containing each of water and ethylene glycol as a solvent
at a concentration of 50% by mass at a liquid temperature of
25.degree. C. using a plate of an alloy of titanium and zirconium
(Ti:Zr=30:70 (atomic ratio), 20 mm long.times.10 mm wide.times.0.1
mm thick) as an anode to obtain a dielectric. The results are shown
in Table 1.
Example 5
[0055] 100 V anodization was performed in a solution containing
phosphoric acid as an electrolyte at a concentration of 0.01% by
mass and containing each of water and ethylene glycol as a solvent
at a concentration of 50% by mass at a liquid temperature of
25.degree. C. using a plate of an alloy of titanium and zirconium
(Ti:Zr=90:10 (atomic ratio), 20 mm long.times.10 mm wide.times.0.1
mm thick) as an anode to obtain a dielectric. The results are shown
in Table 1.
Example 6
[0056] A plate of an alloy of titanium and zirconium (Ti:Zr=40:60
(atomic ratio), 20 mm long.times.10 mm wide.times.0.1 mm thick) was
heat-treated in a mixed gas of methane and Ar (methane:Ar=10:90
(molar ratio)) at 900.degree. C. for 30 minutes to react some of
carbon atoms included in the methane with the alloy plate. Then,
100 V anodization was performed in an aqueous solution containing
phosphoric acid as an electrolyte at a concentration of 0.01% by
mass at a liquid temperature of 25.degree. C. using the alloy plate
as an anode to obtain a dielectric. The results are shown in Table
1.
Example 7
[0057] 1 Part by mass of a polyvinyl alcohol resin as an organic
binder was added to 100 parts by mass of a powder of an alloy of
titanium and zirconium (Ti:Zr=40:60 (atomic ratio)) to fabricate
agglomerates of the alloy powder. A die was filled with the
agglomerates together with metal wire containing an alloy of
titanium and zirconium, and they were pressure-press formed to
fabricate a press formed body having an outer shape of 2.2
mm.times.1.7 mm.times.1.2 mm. Next, the press formed body was
sintered in a vacuum at a high temperature of 600.degree. C. for 30
minutes to obtain a porous sintered body. At this time, most of the
polyvinyl alcohol resin added as the organic binder was pyrolyzed
and discharged as a gas, but the remainder reacted with the alloy
powder and remained. 100 V anodization was performed in an aqueous
solution containing phosphoric acid as an electrolyte at a
concentration of 0.01% by mass at a liquid temperature of
25.degree. C. using the porous sintered body as an anode to obtain
a dielectric. The results are shown in Table 1.
Example 8
[0058] 10 Parts by mass of a styrenic resin as an organic binder
was added to 100 parts by mass of a powder of an alloy of titanium
and zirconium (Ti:Zr=40:60 (atomic ratio)) to fabricate
agglomerates of the alloy powder. A die was filled with the
agglomerates together with metal wire containing an alloy of
titanium and zirconium, and they were pressure-press formed to
fabricate a press formed body having an outer shape of 2.2
mm.times.1.7 mm.times.1.2 mm. Next, the press formed body was
sintered in a vacuum at a high temperature of 600.degree. C. for 30
minutes to obtain a porous sintered body. At this time, most of the
styrenic resin added as the organic binder was pyrolyzed and
discharged as a gas, but the remainder reacted with the alloy
powder and remained. 100 V anodization was performed in an aqueous
solution containing phosphoric acid as an electrolyte at a
concentration of 0.01% by mass at a liquid temperature of
25.degree. C. using the porous sintered body as an anode to obtain
a dielectric. The results are shown in Table 1.
Example 9
[0059] 2 Parts by mass of camphor as an organic binder was added to
100 parts by mass of a powder of an alloy of titanium and zirconium
(Ti:Zr=40:60 (atomic ratio)) to fabricate agglomerates of the alloy
powder. A die was filled with the agglomerates together with metal
wire containing an alloy of titanium and zirconium, and they were
pressure-press formed to fabricate a press formed body having an
outer shape of 2.2 mm.times.1.7 mm.times.1.2 mm. Next, the press
formed body was sintered in a vacuum at a high temperature of
600.degree. C. for 30 minutes to obtain a porous sintered body. At
this time, most of the camphor added as the organic binder was
pyrolyzed and discharged as a gas, but the remainder reacted with
the alloy powder and remained. 100 V anodization was performed in
an aqueous solution containing phosphoric acid as an electrolyte at
a concentration of 0.01% by mass at a liquid temperature of
25.degree. C. using the porous sintered body as an anode to obtain
a dielectric. The results are shown in Table 1.
Comparative Example 1
[0060] A die was filled with a powder of an alloy of titanium and
zirconium (Ti:Zr=40:60 (atomic ratio))together with metal wire
containing an alloy of titanium and zirconium, and they were
pressure-press formed to fabricate a press formed body having an
outer shape of 2.2 mm.times.1.7 mm.times.1.2 mm. Then, a dielectric
was fabricated as in Example 1 using the press formed body. The
results are shown in Table 1.
Comparative Example 2
[0061] 100 V anodization was performed in an aqueous solution
containing phosphoric acid as an electrolyte at a concentration of
0.01% by mass at a liquid temperature of 25.degree. C. using a
plate of an alloy of titanium and zirconium (Ti:Zr=40:60 (atomic
ratio), 20 mm long.times.10 mm wide.times.0.1 mm thick) as an anode
to obtain a dielectric. The results are shown in Table 1.
Comparative Example 3
[0062] A dielectric was fabricated as in Example 3 except that a
plate of an alloy of titanium and zirconium (Ti:Zr=20:80 (atomic
ratio), 20 mm long.times.10 mm wide.times.0.1 mm thick) was used as
the alloy plate. The results are shown in Table 1.
Comparative Example 4
[0063] A dielectric was fabricated as in Example 3 except that a
zirconium plate (Ti:Zr=0:100 (atomic ratio), 20 mm long.times.10 mm
wide.times.0.1 mm thick) was used instead of the alloy plate. The
results are shown in Table 1.
Comparative Example 5
[0064] A plate of an alloy of titanium and zirconium (Ti:Zr=40:60
(atomic ratio), 20 mm long.times.10 mm wide.times.0.1 mm thick) was
heat-treated in a mixed gas of methane and Ar (methane:Ar=50:50
(molar ratio)) at 900.degree. C. for 30 minutes to react some of
carbon atoms included in the methane with the alloy plate. Then,
100 V anodization was performed in an aqueous solution containing
phosphoric acid as an electrolyte at a concentration of 0.01% by
mass at a liquid temperature of 25.degree. C. using the alloy plate
as an anode to obtain a dielectric. The results are shown in Table
1.
Comparative Example 6
[0065] A dielectric was fabricated as in Example 3 except that a
titanium plate (Ti:Zr=100:0 (atomic ratio), 20 mm long.times.10 mm
wide.times.0.1 mm thick) was used instead of the alloy plate. The
results are shown in Table 1.
TABLE-US-00001 TABLE 1 Leakage current after anodization Concen-
(converted Rate of tration value with change Rate of Ti/ of carbon
1.00 in of change of (Zr + Ti) atoms Comparative leakage capaci-
(%) (ppm) Example 2) current tance Example 1 40 4000 0.57 1.6 1.12
Example 2 40 2000 0.30 1.7 1.13 Example 3 40 3000 0.20 1.8 1.18
Example 4 30 3000 0.70 1.7 1.16 Example 5 90 3000 0.80 1.8 1.17
Example 6 40 9000 0.80 1.6 1.19 Example 7 40 5000 0.65 1.6 1.15
Example 8 40 8000 0.72 1.8 1.18 Example 9 40 4000 0.61 1.6 1.14
Comparative 40 70 1.00 2.6 1.47 Example 1 Comparative 40 50 1.00
3.3 1.53 Example 2 Comparative 20 3000 6.00 2.1 1.80 Example 3
Comparative 0 3000 7.00 2.2 1.90 Example 4 Comparative 40 15000
2.00 2.5 1.70 Example 5 Comparative 100 3000 12.00 2.4 1.80 Example
6
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